Certain N-arylhalopyrrolidones are known to be useful as herbicides of general application. Such compounds and their utility are disclosed in, for instance, U.S. Pat. No. 4,110,105 of Eugene G. Teach.
One process for their production is disclosed in U.S. Pat. No. 4,110,105 and additionally U.S. Pat. No. 4,210,589, which is a division of the former. According to those references, the compounds are prepared by the intramolecular cyclization of an .alpha.-halogen-containing N-2-alkenylamide in the presence of a catalytic amount of ferrous iron.
Another U.S. Pat. No. 4,132,713, of Michael D. Broadhurst, discloses an improved method of producing such compounds utilizing catalysts other than ferrous iron. In particular, the catalyst of U.S. Pat. No. 4,132,713 contains one or more of the transition metals vanadium, molybdenum, ruthenium, silver, and copper. The metal-containing compounds may be present in a number of forms, including complexes with common complexing agents such as triphenylphosphine, carbon monoxide, and tertiary amines. Examples of tertiary amines disclosed to be useful in that process are pyridine, 2,2'-dipyridyl, 2,2'-dipyridylamine, and tetramethylethylenediamine. Among the copper-containing compounds specifically disclosed in that patent are cuprous chloride and cupric oxide.
When using copper-containing catalysts with tertiary amine complexing agents, the process may be conducted at a temperature of from about 60.degree. C. to about 200.degree. C., preferably from about 80.degree. C. to about 150.degree. C. Table II of U.S. Pat. No. 4,132,713 shows the results for production of the compound 3-chloro-4-chloromethyl-1-(m-trifluoromethylphenyl)-2-pyrrolidone, ##STR1## utilizing cupric oxide and cuprous chloride variously complexed with several tertiary amines. The process was conducted at times ranging from 2.5 to 11 hours with yields ranging up to 65% of theoretical. A larger scale preparation of the product is described in Example 14 of the patent. Other examples show production of related compounds by this technique.